Variability in physiological responses of Venezuelan cacao to drought

Abstract

In order to assess the response of cocoa trees to drought, changes in water status, gas exchange, leaf carbon isotopic ratio (δ13C), photochemical activity, and leaf N and chlorophyll content during the rainy and dry season were measured in 31 Venezuelan cocoa clones (17 Trinitarios, 6 Criollos, and 8 Modern Criollos) grown in a common garden. Drought caused a 40% decrease in water potential (ψ) in all but the Modern Criollos, and a reduction in net photosynthetic rate (A) and stomatal conductance (gs) without an increase in instantaneous water use efficiency (WUE) in 93% of clones, and an increase in δ13C (long-term WUE) in 74% of clones; these responses suggest differences in tolerance to drought among clones. A positive correlation between A and both gs and leaf N content was found for all genotypes. Leaf N content, chlorophyll content, and photochemical activity were reduced during drought, suggesting that metabolism was also inhibited. The best performance during drought was shown by Modern Criollos with the highest WUE, while five Trinitario clones seemed to be less sensitive to drought, since neither chlorophyll, N, total soluble protein concentration, nor gs changed with drought, indicating that those Trinitario clones, with lower A, have a conservative water use. Modern Criollos showed no reductions in either ψ or gs; A remained unchanged, as did WUE, which was the highest, suggesting that these clones would be more successful in environments with low water availability. Our results indicate large variation in physiological response to drought over a range of parameters, suggesting possible differences in tolerance among clones.

Silicon dioxide nanofertilizers improve photosynthetic capacity of two Criollo cocoa clones (Theobroma cacao L.)

“…The average A values obtained in OC-61 and BR-05 agreed with those previously reported in different varieties and cocoa clones in Venezuela and elsewhere (A between 0.5 and 7 μmol m -2 s -1 ) (Ávila-Lovera et al, 2016(Ávila-Lovera et al, , 2021Bertolde et al, 2012;Daymond et al, 2011;De Almeida et al, 2018;Tezara et al, 2016Tezara et al, , 2020. The results observed in A coincide with the increase in leaf N and P concentration due to treatment.…”

“…Specific leaf area (SLA) was calculated as the ratio between leaf area and dry mass in seven individuals per clone using a protocol described by Tezara et al (2020).…”

“…There is an interest in studying ecophysiological traits in some Venezuelan cocoa clones (Ávila-Lovera et al, 2016(Ávila-Lovera et al, , 2021De Almeida et al, 2018;Tezara et al, 2016Tezara et al, , 2020. However, the effect of specific NF, using SiO 2 nanoparticles as nutrients vehicle (SiO 2 -NF), on the physiological traits of cocoa plants is largely unknown.…”

Actividad fotosintética y su relación con el rendimiento de diez clones de cacao nacional

“…Las A y gs, fueron altas en comparación con las previamente reportados en cacao forasteros y criollos en la literatura (Daymond et al, 2011;Acheampong et al, 2013;Ávila-Lovera et al, 2016;Tezara et al, 2016Tezara et al, , 2020.…”

“…Las A y conductancias estomáticas (gs) reportadas de los diferentes clones de cacao cultivados en invernadero y en campo son bajas, y varían entre 3 a 7 µmol m -2 s -1 y 50 a 120 mmol m -2 s -1 , respectivamente (Daymond et al, 2011;Acheampong et al, 2013;Tezara et al, 2020). Se ha reportado que el cacao muestra una alta sensibilidad al déficit hídrico del suelo (Tezara et al, 2016(Tezara et al, , 2020) y a alta densidad de flujo fotónico (DFF) entre otros estreses abióticos (De Almeida et al, 2018).…”